Hypergolic propellants are characterized by spontaneous reaction upon component mixing and high energy yield per unit mass. As a result of these characteristics, hypergolic propellants are commonly used to power spacecraft, tactical missiles and reactive thruster controllers.
Many conventional hypergolic fuel-oxidizer combinations have the desirable properties of high energy density per unit mass, high specific impulse and short ignition delays. Unfortunately, many of the hypergolic fuels having these properties are derived from hydrazine and include monomethylhydrazine (MMH), unsymmetrical dimethylhydrazine, or combinations thereof. As hydrazines as a class are acutely toxic and suspected carcinogens, costly safety precautions and handling procedures are required. (E. W. Schmidt. Hydrazine and Its Derivatives: Preparation, Properties, and Applications. New York, N.Y.: John Wiley & Sons, Inc., 2001).
Various 2-azidoethanamines have been synthesized and evaluated as potential non-carcinogenic hypergolic fuel compounds. (D. M. Thompson et al. “Hypergolic Azide Liquid Fuels.” Proceedings of the 1998 JANNAF Propulsion Meeting, CPIA Publication 675, vol. III, pp. 515–523, 1998.). Within the class of 2-azidoethanamines, 2-azido-N,N-dimethylethanamine (DMAZ), having the structure (CH3)2NCH2CH2N3, appears to be one of the better candidates. DMAZ yields performance comparable to a fifty—fifty mixture by weight of hydrazine and unsymmetrical dimethylhydrazine in inhibited red fuming nitric acid (IRFNA) oxidized experimental systems. However, DMAZ-IRFNA systems do not meet higher performance standards set by monomethylhydrazine-IRFNA systems, the primary shortcoming being a longer ignition delay. A longer ignition delay results in a greater accumulation of unreacted propellant in the combustion chamber prior to ignition. When the unreacted propellant finally ignites, it produces a pressure transient proportional to the amount accumulated. Therefore, to avoid rupturing the combustion chamber, the chamber must be sized to accommodate the expected transient. Since rocket performance is degraded by larger combustion chamber sizes, shorter ignition delays, leading to smaller propellant accumulations, are desirable. To date, the class of 2-azidoethanamines has not yielded an acceptable substitute for hydrazine-based hypergolic propellants. Thus, there still exists a need for a non-carcinogenic fuel that has energy density, specific impulse and ignition delay characteristics associated with hydrazine compounds.